1. Field of the Invention
This invention relates generally to electronic security methods which provide for modeling or otherwise comparing human features such as fingerprints, voice patterns, and retina patterns, in order to distinguish between individuals, and, more particularly, to a security method and protocol for modeling and comparing voice utterances to control the operation of a security device.
2. Description of Related Art
The following art defines the present state of this field:
Parra, U.S. Pat. No. 5,313,556 describes the identity of an individual (known or unknown) that is determined by a sonic profile of sounds issued through his oral-nasal passages. The sounds are converted to digital electrical signals and produce a three domain format of frequency, amplitude and time samples to produce an array of peaks and valleys constituting the sonic profile of an individual. A source or library of sonic profiles in the same format of a known individual have a interrelationship including relative positions of said peaks and valleys of said sonic profile of the known individual with that of said unknown individual compared and a utilization signal is provided upon detecting or non-detecting a correlation between said sonic profiles.
Hair et al., U.S. Pat. No. 3,673,331 describes voice verification that is accomplished at a plurality of spaced apart facilities each having a plurality of terminals. Multiplexing structure interconnects the terminals through a communications link to a central processing station. Analog reproductions of voices transmitted from the terminals are converted into digital signals. The digital signals are transformed into the frequency domain at the central processing station. Predetermined features of the transformed signals are compared with stored predetermined features of each voice to be verified. A verify or non-verify signal is then transmitted to the particular terminal in response to the comparison of the predetermined features.
Waterbury, U.S. Pat. No. 3,896,266 describes a security card (which may be a credit card) according to the invention has recorded on it data identifying a personal and non-counterfeitable attribute, such as the voice characteristics, of the authorized holder of the card. A card utilization system according to the invention provides means for comparing the attribute as recorded by these data with the corresponding attribute of the person wishing to use the card, thereby substantially eliminating the possibility of unauthorized card utilization.
Muroi et al., U.S. Pat. No. 4,833,713 describes a voice or sound recognition system including a microphone for converting a voice into an electrical voice signal, a frequency analyzer for generating a voice pattern in the form of a time-frequency distribution, and a matching unit for matching the voice pattern with registered voice patterns.
Feix et al., U.S. Pat. No. 4,449,189 describes a method and an apparatus for identifying an individual through a combination of both speech and face recognition. The voice signature of an interrogated person uttering a key word into a microphone is compared in a pattern matcher with the previously stored voice signature of a known person uttering the same key word to obtain a first similarity score. At the same time, when a key event in the utterance of the key word by the interrogated person occurs, a momentary image of that person""s mouth region onto which a grid pattern has been projected is optically recorded and compared with the previously stored corresponding momentary image of the same known person to obtain a second similarity score.
The prior art teaches the comparing of voice signatures in time as well as frequency domain. However, the prior art does not teach a means for filtering such voice profiles by difference techniques. The present invention method fulfills these needs and provides further related advantages as described in the following summary.
The present invention teaches certain benefits in methods which give rise to the objectives described below.
The present invention is a security method which compares a present verbal utterance with a previously recorded (enrollment) verbal utterance by comparing frequency domain representations of the present utterance, with previously recorded multiply repeated utterances of the same material, forming a basis for comparison. Instead of comparing the utterances in the time domain, as is conventional, the present method approaches the comparison by establishing energy content in a variety of cells across the frequency domain, and instead of focusing on the ability of an individual to repeat an utterance from one trial to the next, sometimes separated by days, weeks or even longer, the present approach focuses on the variability of the difference between multiple utterances of the same words or phrases. Specifically, the method attempts to determine if two sounds were produced by the same human voice in an attempt to discriminate between allowed and non-allowed personnel seeking to operate a secure device such as an access lock. Further, the method may be used to determine what command is being given by the individual, culling out the selected command from a library of such commands all uttered by the same individual.
The present method invention has as an important aspect, the discrimination between, and, or matching of a presently uttered verbal word or phrase with the same utterance stored in a library of such utterances. Another aspect of the present method is the achievement of high accuracy and fast results in discrimination and, or matching of verbal utterances by using a difference method for comparison. The present method is a non-obvious and highly effective procedure for extremely high speed comparison of large data sets against a challenge so as to provide the convenience, for instance, of verbal only challenges at a secure door used by a large number of individuals with separate verbal access codes, wherein the delay time for approval has been shown to be in the range of a few seconds or less. The method also results in an extraordinary level of discrimination between individuals while providing a high level of xe2x80x9cforgivenessxe2x80x9d for the normal changes and variations in tone, timber and volume of the human voice from time to time. The discrimination capability of the present method provides a high enough level of confidence for use in military as well as industrial applications, and is inexpensive and simple to use so as to find application in residential use, commercial use and in consumer electronic devices and toys. A further aspect of the present method is the use of testing for minimum energy levels in a set of frequency ranges in the frequency domain, as well as testing for corresponding energy levels that surpass a selected energy level criterion. Other features and advantages of the present invention will become apparent from the following more detailed description providing an understanding of the principles of the invention.